System-level optimization and design of the high speed machining process using ceramic cutting tools

Research on ceramic cutting tools is interdisciplinary, straddling across engineering studies of stress analysis and heat transfer and materials science studies of microstructure-property relationships. A systems analysis methodology is used to investigate the linkages between these two disciplines. System-level partitioning of the functional relationships has identified three key linking variables: hardness, temperature and thermal diffusivity. The linking variables are used to estimate the flash temperature existing at the cutting interface. The flash temperature depends on the interaction between the change in the intrinsic hardness of the ceramic material with temperature and the influence of material hardness on the heat generated at the cutting interface. This information is used to construct process performance diagrams which may be useful in optimizing wear rate in the ceramic cutting tool against material removal rate and surface finish. The results are applied to two kinds of ceramic cutting tools: alumina and titanium carbide. The work piece is assumed to be AISI 4340 steel. The study highlights three key problems in materials science that need to be addressed in order to extend the microscopic understanding of materials to ceramic grinding and machining processes: (i) micromechanistic understanding of temperature-dependence of hardness of ceramics; (ii) micromechanisms of wear and thermal shock behavior in the local, strongly varying temperature fields near the contact area between the tool and the work piece; and (iii) microstructural understanding of thermal conductivity of cutting tool materials.